The present invention is to provide an electron gun of a monochromic CRT comprising at least two electron emission sources (e.g., cathodes) for emitting beams having a small beam spot size and being adapted to impinge on the same spot of a screen of the monochromic CRT after having been focused by a focusing lens or common lens in the electron gun. As an end, the resolution, focusing quality and brightness of the screen of the monochromic CRT are improved.